The present invention relates to solid state lasers and the manufacture of same. More particularly, the present invention relates to mounting a laser rod tube into a pumping chamber of a solid state laser.
It is common practice in the laser industry to attach a laser rod tube to the end of a laser rod. Such tubes provide a convenient means for handling the rod and fixing it into a pumping chamber assembly of a solid state laser.
To be effective, the laser rod tube must be securely attached to the laser rod. Solid state lasers are typically water-cooled, so the joint between the rod tube and the laser rod must also be leak tight.
Because the joint area is exposed to laser radiation, common seal materials, such as the elastomers used in O-rings or adhesives, can be damaged by this radiation. This in turn often results in seal failures or contamination of the laser rod faces by the material given off by the seal.
It is known that PTFE (Teflon(trademark)) is a material that is highly resistant to damage by laser radiation. Based on this knowledge, it has been previously proposed to use PTFE as a sealing material for the joint between the rod tube and the laser rod in order to avoid the seal failures and/or contamination of the laser rod faces experienced when common seal materials are used to seal the joint.
However, PTFE seals are difficult to compress. Attempts to use traditional techniques to form a compression joint between the rod tube and the laser rod with a PTFE seal have been unsuccessful. This has been due to the inability, using such techniques, to sufficiently compress the PTFE seal so as to achieve reliable leak tight sealing at the joint.
Accordingly, more recently developed techniques, such as those using two part threaded rod tubes or flanged clamps, have been proposed to compress the PTFE seal to form the required compression joint between the rod tube and the laser rod. However, even using these techniques, space constraints around the laser rod end make it difficult to achieve the necessary forces required to compress the PTFE seal and thereby form an effective long term leak tight joint between the rod tube and the laser rod. Furthermore, even where these techniques can be used successfully to initially form a leak tight joint between the rod tube and the laser rod, subsequent cold flow of the PTFE can lead to seal failures over time.
Accordingly, a need exists for a simple, effective technique to mount a laser rod tube into a pumping chamber of a solid state laser such that a leak tight joint is formed between the rod tube and the laser rod and previously experienced problems are avoided.
While the invention is described below with reference to preferred embodiment(s), it should be understood that the invention is not limited thereto. Those of ordinary skill in the art having access to the teachings herein will recognize additional implementations, modifications, and embodiments, as well as other fields of use, which are within the scope of the invention as disclosed and claimed herein and with respect to which the invention could be of significant utility.
In accordance with the invention, a laser rod is mounted to a laser rod tube, by inserting an end of a laser rod into an end portion of a laser rod tube. The laser rod tube end portion has an inner diameter larger than the outer diameter of the laser rod. Preferably, the inner diameter of the portion of the laser rod tube adjacent to the laser rod tube end portion is smaller than the inner diameter of the end portion. Typically, this adjacent portion of the tube extends for the remainder of laser rod tube and forms the primary portion of the tube.
One or more seal rings, preferably three Teflon(trademark) seal rings, are inserted into the laser rod tube end portion so as to be disposed between the inner diameter of the laser rod tube end portion and the outer diameter of the inserted laser rod end. Beneficially, each seal ring has a substantially square cross section, and a chamfered outer diameter to make it easier to insert into the tube. It is beneficial that each seal ring has an interference fit between its inner diameter and an outer diameter of the laser rod. Additionally an interference fit between the outer diameters of each seal ring will beneficially have an interference fit with the inner diameter of the laser rod tube end portion such that a pressing force is applied to press the seal rings between the laser rod and the laser rod tube.
With the rod and seal ring(s) inserted, the laser rod tube end portion is deformed or swaged to compress the inserted seal ring(s). Preferably, with the seal ring(s) inserted, the laser rod tube end portion extends beyond the inserted seal ring(s), in the opposite direction to that in which the laser rod end extends into the laser rod tube. This extended portion of the tube end portion is commonly referred to as the lip. The lip is typically swaged to enclose the seal ring(s) completely within the laser rod tube, and form a leak proof seal between the laser rod tube and the laser rod. A swaging force is applied which is sufficient to compress the seal ring(s).
The result is an assembly, in which the laser rod end is located within a laser rod tube, with at least one seal ring disposed between the laser rod tube and the laser rod in a swaged end portion of the laser rod tube. Beneficially, each seal ring in the assembly is made of Teflon(trademark), has a chamfered outer diameter, and has a substantially square cross section. The seal ring(s) within the assembly are preferably compressed and form a leak proof seal between the laser rod tube and the laser rod, with the swaged end portion completely enclosing the seal ring(s) within the laser rod tube.
In a practical implementation of the invention a solid state laser may be formed by providing laser pump chamber formed within a chamber housing. The laser includes at least one flash lamp disposed within the chamber for pumping at least one laser rod disposed within the chamber for being pumped by the flash lamp. Within the chamber there is provided at least one swaged seal joint compressing at least one Teflon seal ring disposed within the chamber and the at least one swaged seal joint may be used at any joint where a high reliability leak proof radiation resistant seal my be required. The chamber may further include at least one reflector for reflecting flash lamp radiation onto the laser rod and the chamber may be dry or flooded with a cooling fluid for cooling elements disposed therein. In a particularly beneficial implementation each laser rod within the chamber includes two opposing ends. A laser rod tube is attached at each end of the laser rod for supporting the laser rod and for keeping the end face of the laser rods protected. In this case each laser rod tube is attached to the laser rod by swaged seal joint compressing three square cross-sectional Teflon seal rings.
The swaged seal joint is easily adapted for use in other applications. For example, the swaged seal joint can be used to seal a flow tube and end block in a pumping chamber. The joint can also be easily adapted to uses outside the field of solid state lasers. Thus, those skilled in the art will recognize that any rod type structure and tube type structure could be substituted for the laser rod and laser rod tube described herein and should be considered equivalents thereto for purposes of this invention.